Accommodating intraocular lenses

ABSTRACT

An accommodating intraocular lens includes an optic portion a haptic portion and a backstop. The optic portion of the lens includes an actuator that deflects a lens element to alter the optical power of the lens responsive to forces applied to the haptic portion of the lens by contraction of the ciliary muscles. Forces applied to the haptic portion may result in fluid displacements from or to the haptic portion from the actuator. The backstop provides support to the haptic so that bulk translation of the haptic is prevented in response to the forces applied by the capsular sac.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/193,487, filed Jul. 28, 2011, which is a continuation of U.S.application Ser. No. 11/642,388, filed Dec. 19, 2006, now U.S. Pat. No.8,361,145, the disclosures of which are hereby incorporated by referencein their entirety.

FIELD

The present invention relates to intraocular lenses (“IOLs”) havingoptical parameters that are changeable in-situ. More particularly, theinvention has application in IOLs for in-capsule implantation forcataract patients or presbyopic patients, wherein movement of the lenscapsule applies forces to a circumferentially supported haptic to moreefficiently induce transfer of fluid media within the interior of theIOL to alter an optical power of the lens.

BACKGROUND

Cataracts are a major cause of blindness in the world and the mostprevalent ocular disease. Visual disability from cataracts accounts formore than 8 million physician office visits per year. When thedisability from cataracts affects or alters an individual's activitiesof daily living, surgical lens removal with intraocular lens (IOL)implantation is the preferred method of treating the functionallimitations. In the United States, about 2.5 million cataract surgicalprocedures are performed annually, making it the most common surgery forAmericans over the age of 65. About 97 percent of cataract surgerypatients receive intraocular lens implants, with the annual costs forcataract surgery and associated care in the United States being upwardsof $4 billion.

A cataract is any opacity of a patient's lens, whether it is a localizedopacity or a diffuse general loss of transparency. To be clinicallysignificant, however, the cataract must cause a significant reduction invisual acuity or a functional impairment. A cataract occurs as a resultof aging or secondary to hereditary factors, trauma, inflammation,metabolic or nutritional disorders, or radiation. Age-related cataractconditions are the most common.

In treating a cataract, the surgeon removes the crystalline lens matrixfrom the lens capsule and replaces it with an intraocular lens (“IOL”)implant. The typical IOL provides a selected focal length that allowsthe patient to have fairly good distance vision. Since the lens can nolonger accommodate, however, the patient typically needs glasses forreading.

More specifically, the imaging properties of the human eye arefacilitated by several optical interfaces. A healthy youthful human eyehas a total power of approximately 59 diopters, with the anteriorsurface of the cornea (e.g. the exterior surface, including the tearlayer) providing about 48 diopters of power, while the posterior surfaceprovides about −4 diopters. The crystalline lens, which is situatedposterior of the pupil in a transparent elastic capsule supported by theciliary muscles via zonules, provides about 15 diopters of power, andalso performs the critical function of focusing images upon the retina.This focusing ability, referred to as “accommodation,” enables imagingof objects at various distances.

The power of the lens in a youthful eye can be adjusted from 15 dioptersto about 29 diopters by adjusting the shape of the lens from amoderately convex shape to a highly convex shape. The mechanismgenerally accepted to cause this adjustment is that ciliary musclessupporting the capsule (and the lens contained therein) move between arelaxed state (corresponding to the moderately convex shape) and acontracted state (corresponding to the highly convex shape). Because thelens itself is composed of viscous, gelatinous transparent fibers,arranged in an “onion-like” layered structure, forces applied to thecapsule by the ciliary muscles via the zonules cause the lens to changeshape.

Isolated from the eye, the relaxed capsule and lens take on a morespherical, or more convex, shape. Within the eye, however, the capsuleis connected around its circumference by approximately 70 tiny ligamentfibers to the ciliary muscles, which in turn are attached to an innersurface of the eyeball. The ciliary muscles that support the lens andcapsule therefore are believed to act in a sphincter-muscular mode.Accordingly, when the ciliary muscles are relaxed, the capsule and lensare pulled about the circumference to a larger diameter, therebyflattening the lens, whereas when the ciliary muscles are contracted thelens and capsule relax somewhat and assume a smaller diameter thatapproaches a more spherical shape (i.e., more convex shape).

As noted above, the youthful eye has approximately 14 diopters ofaccommodation. As a person ages, the lens hardens and becomes lesselastic, so that by about age 45-50, accommodation is reduced to about 2diopters. At a later age the lens may be considered to benon-accommodating, a condition known as “presbyopia”. Because theimaging distance is fixed, presbyopia typically entails the need forbi-focals to facilitate near and far vision.

Apart from age-related loss of accommodation ability, such loss isinnate to the placement of IOLs for the treatment of cataracts. IOLs aregenerally single element lenses made from a suitable polymer material,such as acrylics or silicones. After placement, accommodation is nolonger possible, although this ability is typically already lost forpersons receiving an IOL. There is significant need to provide foraccommodation in IOL products so that IOL recipients will haveaccommodating ability.

Although previously known workers in the field of accommodating IOLshave made some progress, the relative complexity of the methods andapparatus developed to date have prevented widespread commercializationof such devices. Previously known devices have proved too complex to bepractical to construct or have achieved only limited success, due to theinability to provide accommodation of more than 1-2 diopters.

U.S. Pat. No. 5,443,506 to Garabet describes an accommodatingfluid-filled lens wherein electrical potentials generated by contractionof the ciliary muscles cause changes in the index of refraction of fluidcarried within a central optic portion. U.S. Pat. No. 4,816,031 to Pfoffdiscloses an IOL with a hard poly methyl methacrylate (PMMA) lensseparated by a single chamber from a flexible thin lens layer that usesmicrofluid pumps to vary a volume of fluid between the PMMA lens portionand the thin layer portion and provide accommodation. U.S. Pat. No.4,932,966 to Christie et al. discloses an intraocular lens comprising athin flexible layer sealed along its periphery to a support layer,wherein forces applied to fluid reservoirs in the haptics vary a volumeof fluid between the layers to provide accommodation.

Although fluid-actuated mechanisms such as described in theaforementioned patents have been investigated, currently availableaccommodating lenses include the Crystalens developed by Eyeonics, Inc.(formerly C&C Vision, Inc.) of Aliso Viejo, Calif. According toEyeonics, redistribution of the ciliary mass upon constriction causesincreased vitreous pressure resulting in forward movement of the lens.

Co-pending, commonly assigned U.S. Patent Application Publication No.2005/0119740 to Esch et al., which is incorporated by reference hereinin its entirety, describes an intraocular lens in which forces appliedby the lens capsule to a haptic portion of the lens to induce fluidtransfer to and from an actuator disposed in contact with a dynamicsurface of the lens.

While the lens described in the foregoing Esch application is expectedto provide significant benefits over previously-known accommodating lensdesigns, it would be desirable to provide methods and apparatus forfurther enhancing conversion of lens capsule movements into hydraulicforces, so as to improve modulation of the lens actuator and dynamicsurface.

It also would be desirable to provide methods and apparatus to enhancethe efficiency with which loads arising due to natural accommodatingmuscular action are converted to hydraulic forces.

SUMMARY OF THE DISCLOSURE

In view of the foregoing, it is an object of the present invention toprovide apparatus and methods that restore appropriate optical focusingpower to the human eye.

It is a further object of this invention to provide methods andapparatus wherein a dynamic lens surface may be hydraulicallymanipulated responsive to movement of the ciliary muscles and lenscapsule.

It also is an object of the present invention to provide methods andapparatus for further enhancing conversion of lens capsule movementsinto hydraulic forces, so as to improve modulation of the lens actuatorand dynamic surface.

It is another object of this invention to provide methods and apparatusto enhance the efficiency with which loads arising due to naturalaccommodating muscular action are converted to hydraulic forces.

These and other objects of the present invention are accomplished byproviding an intraocular lens responsive to forces communicated from theciliary muscles through the zonules to the capsular bag to operate oneor more actuators disposed within the IOL. The actuator is coupled to adynamic surface of the IOL to deflect the dynamic surface, e.g., from amoderately convex to a highly convex shape, responsive to operation ofthe one or more actuators.

In accordance with the principles of the present invention, the IOLincludes at least one fluid-mediated actuator coupled to a fluid columndisposed in at least one haptic of the IOL and a haptic supportstructure, or backstop, supporting at least a portion of the haptic.Forces applied to the haptic by the capsular bag, responsive to movementof the ciliary muscles, cause the transfer of fluid between the fluidcolumn and the actuator, which in turn deflects a dynamic surface of thelens. As used herein, a “backstop” is a structure that opposes theforces applied by the capsular sac and limits or prevents bulktranslation of the entire haptic in response to those forces so that theforce may be converted more efficiently into deformation of the haptic.The backstop may be integrated into an optic portion or a haptic portionof the IOL or a separate structure.

In a preferred embodiment, the intraocular lens comprises an opticportion, a haptic (or non-optic) portion and a backstop. The opticportion comprises a light transmissive substrate defining one or morefluid channels, at least one actuator coupled in fluid communicationwith the fluid channels, and anterior and posterior lens elements. Oneof the anterior and posterior lens elements includes a dynamic surfacethat is operatively coupled to the actuator to cause deflection of thedynamic surface. The other of the anterior or posterior lens elementsmay be coupled to the substrate or integrally formed therewith as amonolithic body.

The haptic portion is disposed at the periphery of the optic portion andcomprises one or more haptics that extend outward from the opticportion, each haptic including a fluid channel coupled in fluidcommunication with a fluid channel in the optic portion. In accordancewith one aspect of the present invention, the haptics have across-sectional configuration selected so that the internal volume ofthe haptic is small in an accommodated state. The accommodated state ofthe eye corresponds to the condition when the ciliary muscles arecontracted and anterior/posterior (i.e., axial) compressive forcesapplied by the capsular bag to the haptics are minimal and radialcompressive forces applied by the capsular bag compress the hapticradially toward the optical axis.

When the ciliary muscles relax, the zonules pull the capsular bag tautand apply forces to the anterior and posterior faces of the haptic andreduce the compressive forces applied radially to the haptic. Thebackstop prevents the entire haptic from translating in response tothese forces. The backstop may be configured to resist bulk axial orradial translation of the haptic or combinations thereof. The forcesapplied by the capsular bag in conjunction with the backstop cause thecross-sectional area of the haptic to increase thereby increasing theinternal volume of the haptic. This action in turn causes fluid to bewithdrawn from the actuator disposed in the optic portion, so that thedynamic surface of the IOL transitions from an accommodated state to anunaccommodated state.

The actuator used in the optic portion of the IOL may be centrallylocated within the optic portion that, when filled with fluid, biasesthe dynamic surface of the IOL to the accommodated state. When theciliary muscles are contracted, the zonules and capsular bag are lesstaut, and the haptics are compressed radially toward the optical axis.Relaxation of the ciliary muscle causes the zonules to transition thecapsule to less convex shape, which applies compressive forces to theposterior and anterior faces of the haptic, thereby withdrawing fluidfrom the actuator and causing the lens to transition to theunaccommodated state. Alternatively, the actuator may comprisestructures disposed at the periphery of the optic portion, so as tominimize refractive effects and optical aberrations in the opticportion.

In another embodiment, the backstop is a thin-walled member that iscoupled to a portion of an outer surface of the haptic, radially spacedfrom the optic portion of the IOL. Alternatively, the backstop mayextend radially outward from the optic portion to the haptic portion.The backstop is generally shaped as a portion of a disk or cone, and maybe configured to tangentially support a haptic, or it may be configuredto support a portion of the outer surface of the haptic.

Methods of making and using the lens of the present invention also areprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments, in which:

FIG. 1 is a sectional side view of a human eye;

FIGS. 2A and 2B are, respectively, sectional side views of the lens andsupporting structures of FIG. 1 illustrating relaxed and contractedstates of the ciliary muscles;

FIGS. 3A-3C are, respectively, a perspective, exploded perspective andplan view of an exemplary intraocular lens which may be modified toimplement the structure and methods of the present invention;

FIG. 4 is a cross-sectional view of a haptic of the intraocular lens ofFIG. 3;

FIG. 5 is a cross-sectional view of the assembled intraocular lens ofFIG. 3;

FIGS. 6A-6C are graphical representations of a lens capsule inaccommodated, transition and unaccommodated configurations,respectively;

FIGS. 7A-7D are schematic cross-sectional views of the interactionbetween a lens capsule and an intraocular lens;

FIGS. 8A-8B are, respectively, a perspective view and a cross-sectionalview of an illustrative embodiment of the intraocular lens of thepresent invention;

FIGS. 9A-9B are, respectively, a perspective view and a cross-sectionalview of an alternative embodiment of the intraocular lens of the presentinvention;

FIGS. 10A-10C are cross-sectional schematic views of a backstop and ahaptic, wherein FIGS. 10A and 10B show alternative embodiments in anaccommodated state and FIG. 10C shows an embodiment in an unaccommodatedstate;

FIGS. 11A-11B are, respectively, cross-sectional schematic views of abackstop and a haptic in both accommodated and unaccommodated states;

FIGS. 12A-12D are cross-sectional schematic views of a backstop and ahaptic, wherein FIGS. 12A-12C show alternative embodiments in anaccommodated state and FIG. 12D shows an embodiment in an unaccommodatedstate; and

FIGS. 13A-13B are, respectively, a perspective view and across-sectional view of an alternative embodiment of the intraocularlens of the present invention.

DETAILED DESCRIPTION

In accordance with the principles of the present invention, anintraocular lens is provided having a haptic portion and alight-transmissive optic portion. The optic portion contains one or morefluid-mediated actuators arranged to apply a deflecting force on adynamic surface of the lens to provide accommodation. As used herein,the lens is fully “accommodated” when it assumes its most highly convexshape, and fully “unaccommodated” when it assumes its most flattened,least convex state. The lens of the present invention is capable ofdynamically assuming any desired degree of accommodation between thefully accommodated state and fully unaccommodated state responsive tomovement of the ciliary muscles and lens capsule.

Forces applied to a haptic portion of the intraocular lens by movementof the ciliary muscles and lens capsule are communicated to at least oneactuator that controls deflection of a dynamic surface, which maycomprise an anterior or posterior element of the lens. In accordancewith the principles of the present invention, the haptic portion issupported over at least a portion of its circumference to efficientlyconvert movements of the lens capsule into hydraulic forces suitable formoving the lens actuator. The lens actuator and surrounding fluids allare index-matched to prevent the occurrence of optical aberrations andreflections throughout the range of motion of the actuator and dynamicsurface.

Referring to FIGS. 1 and 2, the structure and operation of a human eyeare first described as context for the present invention. Eye 10includes cornea 11, iris 12, ciliary muscles 13, ligament fibers orzonules 14, capsule 15, lens 16 and retina 17. Natural lens 16 iscomposed of viscous, gelatinous transparent fibers, arranged in an“onion-like” layered structure, and is disposed in transparent elasticcapsule 15. Capsule 15 is joined by zonules 14 around its circumferenceto ciliary muscles 13, which are in turn attached to the inner surfaceof eye 10. Vitreous 18 is a viscous, transparent fluid that fills thecenter of eye 10.

Isolated from the eye, the relaxed capsule and lens take on a highlyconvex shape. However, when suspended within the eye by zonules 14,capsule 15 moves between a moderately convex shape (when the ciliarymuscles are relaxed) and a highly convex shape (when the ciliary musclesare contracted). As depicted in FIG. 2A, when ciliary muscles 13 relax,capsule 15 and lens 16 are pulled about the circumference, therebyflattening the lens. As depicted in FIG. 2B, when ciliary muscles 13contract, capsule 15 and lens 16 relax and become thicker. This allowsthe lens and capsule to assume a more convex shape, thus increasing thediopter power of the lens.

Accommodating lenses that are currently commercially available, such asthe Crystalens device developed by Eyeonics, Inc., Aliso Viejo, Calif.,typically involve converting movements of the ciliary muscle intoanterior and posterior movement of an optic portion of the IOL relativeto the retina. Such devices do not employ the natural accommodationmechanisms described above with respect to FIGS. 1-2, but instead relydirectly on changes in vitreous pressure to translate the lens.

Referring now to FIGS. 3-5, an exemplary embodiment of an intraocularlens suitable for implementing the structure of the present invention isdescribed, such as is described in the commonly assigned U.S. PatentApplication No. 2005/0119740 to Esch et al., which is incorporatedherein by reference. For completeness of disclosure, details of the IOLdescribed in that application are provided below.

IOL 20 comprises optic portion 21 and haptic portion 22. Optic portion21 is constructed of light transmissive materials, while haptic portion22 is disposed at the periphery of the optic portion and does notparticipate in focusing light on the retina of the eye.

Optic portion 21 comprises anterior lens element 23 including actuator24 (see FIG. 5), intermediate layer 25 and posterior lens element 27,also referred to herein as “substrate,” all made of light-transmissivematerials, such as silicone or acrylic polymers or other biocompatiblematerials as are known in the art of intraocular lenses. Illustratively,actuator 24 comprises a bellows structure that is integrally formed withanterior lens element 23. It will be appreciated that actuator 24 mayalternatively be integrally formed with intermediate layer 25, ifdesired. Optic portion 21 is illustratively described as comprisingthree layers, although it will be apparent that other arrangements maybe employed.

Haptic portion 22 illustratively comprises haptics 28 and 29 that extendfrom substrate 27. Each of haptics 28 and 29 includes an interior volume30 that communicates with channel 31 in substrate 27. Actuator 24 isdisposed in well 32 formed in intermediate layer 25 and substrate 27, sothat a lower end of the actuator seats within well 32. Haptics 28 and 29may each include a resilient support member 33 (see FIGS. 4 and 5) thaturges the haptic radially outward to ensure that the haptic seatsagainst the capsular equator.

Although channel 31 and well 32 are depicted in FIG. 5 having their sidewalls disposed parallel to the optical axis of the lens, it is expectedthat all such surfaces may be arranged obliquely relative to the opticalaxis of the IOL. Such an arrangement is expected to reduce the potentialto create spurious reflections in light passing along the optical axisof the IOL. It should be understood that such arrangements may bebeneficially employed throughout the IOLs described in thisspecification.

As depicted in FIG. 4, each of haptics 28 and 29 has an accommodatedstate and may be transitioned to an unaccommodated state (shown indotted line in FIG. 4) by application of compressive forces to theanterior/posterior surfaces of the haptic (shown by arrows A) andreduction of radial compressive forces to the lateral surfaces of thehaptic (shown by arrows B). Haptics 28 and 29 are configured so that theinterior volumes of the haptics increase as the haptics deform from theaccommodated state to the unaccommodated state. The accommodated statedepicted by the solid lines in FIG. 4 corresponds to a fully-contractedstate of the ciliary muscles, as described herein below.

Actuator 24 is disposed in well 31 of intermediate layer 25 andsubstrate 27, and preferably comprises a sturdy elastomeric material.Intermediate layer 25 isolates fluid in channel 31, well 32 and theinterior of actuator 24 from the fluid disposed in the space 34 betweenanterior lens element 23 and intermediate layer 25. Fluids disposedwithin channels 31 and space 34, preferably comprise silicone or acrylicoils or other suitable biocompatible fluids, and are selected to haverefractive indices that match the materials of anterior lens element 23,actuator 24, intermediate layer 25 and posterior lens element, i.e.,substrate 27.

Illustratively, actuator 24 comprises a bellows structure integrallyformed with anterior lens element 23, and is configured to deflectanterior lens element 23 responsive to fluid pressure applied within thebellows by haptics 28 and 29. Alternatively, actuator 24 may befabricated as a separate component and glued or otherwise bonded toanterior lens element 23 and intermediate layer 25.

Deflection of the anterior lens element resulting from movement ofactuator 24 cause the anterior lens element to transition between anaccommodated state, in which the lens surface is more convex, to anunaccommodated state, in which the lens surface is less convex. As willof course be understood, optic portion could instead be arranged so thatactuator 24 deflects posterior lens element 27. Still further, theactuator may be configured to induce a major deflection of one lenselement and a minor deflection of the other lens element; thearrangement depicted in FIG. 3 is intended to be illustrative only.

The inner surface and thickness of anterior element 23 (relative to theoptical axis of the lens) are selected so that the outer surface ofanterior element 23 retains an optically corrective shape throughout theentire range of motion of actuator 24, e.g., for accommodations 0-10diopters. It should of course be understood that the inner surface andthickness of anterior element 23 may be selected to provide anaspherical outer surface, as required for a desired degree of opticalcorrection.

While IOL 20 includes single actuator 24 located at the center of opticportion 21, the IOL alternatively may include an array of actuatorsspaced apart in a predetermined configuration on the posterior surfaceof the anterior lens element, as may be required to impose a desiredpattern of localized deflection on the anterior lens element. As will beapparent to one of skill in the art, an annular structure may besubstituted for the individual actuator depicted in FIG. 5, and the sidewalls of the actuator may be of any suitable shape other than a bellowsstructure. For example, the actuator may comprise a polymer that hadbeen treated, such as by application of bi-axial stress, to pre-orientthe polymer to stretch predominantly in a desired direction.

IOL 20 also may include coating 35 disposed on all interiorfluid-contacting surfaces within the IOL, such as fluid channel 31 andwell 32 and the surfaces defining space 34. Coating 35 is configured toreduce or prevent diffusion of the index-matched fluid used to driveactuator 24, and within space 34, from diffusing into the polymer matrixof the lens components and/or to prevent inward diffusion of externalfluids into the IOL. The IOL also may include coating 36, whichcomprises the same or a different material than coating 35, disposed onthe exterior surfaces of the lens. Coating 36 is intended to serve as abarrier to prevent the diffusion of fluids from the eye into the IOL orfrom the IOL into the eye, and may be disposed on the entire exteriorsurface of the optic portion and haptic portion, including the anteriorand posterior lens elements and haptics.

Alternatively, both coatings 35 and 36 may be layered onto a singlesurface to prevent or reduce both ingress of bodily fluids into the IOLor fluid circuit, and loss of index-matched fluid from the interiorspaces of the IOL. Coatings 35 and 36 preferably comprise a suitablebiocompatible polymer, perfluorinated hydrocarbon, such as PTFE,inorganic (e.g., silicone dioxide) or metallic layer (e.g.,nickel-titanium) applied by any of a variety-of methods known in theart.

Operation of IOL 20 of FIGS. 3-5 is now described. IOL 20 is implantedwithin a patient's capsule after extraction of the native lens using anysuitable technique. When implanted, haptics 28 and 29 support the IOL sothat optic portion 21 is centered along the central axis of eye. Whenthe ciliary muscles are in a contracted state, the zonules are less tautand the capsule places radial compressive force on haptics 28 and 29 andhaptics 28 and 29 are placed in the accommodated state. In thiscondition, fluid pressure applied by the fluid in the haptics, channel31 and well 32 maintain actuator 24 fully extended, so that anteriorlens element 23 is deflected to its accommodated state.

When the ciliary muscles relax, the zonules pull the capsule taut,thereby applying axial compressive forces on the anterior/posteriorsurfaces of the haptics and reducing the radial compressive forces onthe lateral surfaces of the haptics. These force changes cause thehaptics to deform to the unaccommodated state depicted by the dottedlines in FIG. 4, thereby increasing the interior volume of the haptics.Because there is only a predetermined amount of fluid contained withinthe interior of the haptics, channel 31, well 32 and actuator 24, theincreased volume arising in unaccommodated haptics 28 and 29 draws fluidfrom within actuator 24. This in turn causes the actuator to shorten,deflecting anterior lens element 23 to a flatter, unaccommodated state.Subsequent contraction and relaxation of the ciliary muscles causes theforegoing process to repeat, thereby providing a degree of lensaccommodation that mimics the accommodating action of the natural lens.

In the course of developing IOL 20 described above, it was observed thathaptic design created the potential for movement of the entire hapticrelative to the lens capsule and optic portion. It was theorized thatsuch movement in turn might reduce the efficiency by which loads imposedby the lens capsule are converted to the hydraulic forces developedwithin IOL 20. The present invention therefore is directed to structure,which may be implemented in IOL 20, to more efficiently convertmovements of the lens capsule into hydraulic forces for inducingmovement of actuator 24 of the above-described device.

It was expected that because the anterior wall of the human lens capsulegenerally has a greater thickness than that of the posterior wall andmay include more zonular attachments as the eye ages, the lens capsulemay impose asymmetric loads on the IOL when transitioning between theaccommodated and unaccommodated configurations. Accordingly, translationof the anterior wall towards the capsular equator was expected to begreater than that of the posterior wall when the capsule transitionsbetween the unaccommodated and accommodated configurations.

FIGS. 6A-6C illustrate the results of a numerical simulation of a lenscapsule transitioning between the unaccommodated and accommodatedconfigurations responsive to relaxation of ciliary muscles 13. In FIG.6A, lens capsule 10 is fully accommodated and assumes its most highlyconvex shape. Anterior wall 37 extends generally convex upward andposterior wall 38 extends generally convex downward; the anterior andposterior wall portions are joined at equatorial portion 39.

In FIG. 6B, lens capsule 10 is depicted in an intermediate positionbetween the fully accommodated and the fully unaccommodatedconfigurations. In this case anterior wall 37 and posterior wall 38 arepartially retracted towards equatorial portion 39 and equatorial portion39 expands radially outward. As a result, each of anterior wall 37 andposterior wall 38 is less convex than in FIG. 6A.

In FIG. 6C, lens capsule 10 is shown in the fully unaccommodatedconfiguration, with anterior wall 37 and posterior wall 38 furtherretracted toward equatorial portion 39 and equatorial portion 39 furtherexpanded radially outward. The periphery of anterior wall 37, closest toequatorial portion 39, translates a significantly greater distance thanthe peripheral portion of the posterior wall that is equidistant fromequatorial portion 39. As a result, the anterior wall is expected toexert significantly greater force upon a haptic near the equatorialportion 39 of the lens capsule than the posterior wall.

Referring to FIGS. 7A-7D, the interaction between lens capsule 10 andIOL 20 will be described in greater detail. FIG. 7A depicts theinteraction between haptic 29 and lens capsule 10 when lens capsule 10is in an accommodated state, corresponding to FIG. 6A. In such a state,compressive forces applied by lens capsule 10 upon haptic are generallydirected radially inward toward the optical axis of IOL 20, as shown byarrow B. In such a configuration, haptic 29 is compressed betweenequatorial portion 39 of lens capsule 10 and optic portion 21 of IOL 20such that a part of optic portion 21 forms a backstop. It should beappreciated, however, that the backstops disclosed herein may be formedfrom optic portion 21 and/or haptic portion 22 and/or separatestructures.

When lens capsule 10 transitions to an intermediate position, as shownin FIGS. 6B and 7B, the radial force applied by lens capsule 10 onhaptic 29 is reduced and a compressive force applied to theposterior/anterior faces of haptic 29 by lens capsule 10 is increased.It will be appreciated that the during the change in orientation of thecompressive force acting on haptic 29 by lens capsule 10 there may be aperiod during which the volume of haptic 29 remains unchanged. However,that period may be reduced or eliminated, if desired, by tailoring theflexibility of haptic 29 and/or the configuration of a backstop and/orhaptic 29.

Referring to FIG. 7C, lens capsule 10 is shown in a fully unaccommodatedstate. In the unaccommodated state, the radial compressive forcesapplied by lens capsule 10 upon haptic 29 are removed and lens capsuleapplies compressive forces on posterior/anterior faces of haptic 29.Those compressive forces further change the shape of haptic 29 so thatthe interior volume of haptic 29 increases.

As mentioned above, the transition from radial to posterior/anteriorcompressive force applied by lens capsule 10 on haptic 29 may result inan intermediate period of constant interior volume of haptic 29.Referring to FIG. 7D an alternative embodiment of haptic 29 is shownthat includes a flange, or blade, 26. Flange 26 extends radially outwardfrom a lateral surface of haptic 29 and contacts equatorial portion 39of lens capsule 10. Flange 26 increases the radial compression of haptic29 when lens capsule 10 is in an accommodated state. Because of thatincreased radial compression there is a greater change in interiorvolume of haptic 29 that will occur through the same motion of lenscapsule 10. As a result, the period of constant interior volume ofhaptic 29 during the transition from the accommodated to theunaccommodated states may be reduced or eliminated.

Referring now to FIGS. 8A and 8B, an embodiment of an IOL constructed inaccordance with the principles of the present invention is described.IOL 40 seeks to maximize the hydraulic forces generated by theasymmetric loads imposed during transition of the lens capsule betweenthe accommodated and unaccommodated configurations. IOL 40 generallyincludes optic portion 41 and haptic portion 42, both of which aresimilar in construction to the corresponding portions of the embodimentof FIGS. 3-5. In particular, optic portion 41 includes anterior lenselement 43, actuator 44, intermediate layer 45 and substrate 46.

Haptic portion 42 includes haptics 48 and 49, each of which defineinterior volume 50 that is in fluid communication with channels and well52 that are formed in substrate 46. Because the structure of thecomponents is substantially identical to the corresponding structures ofIOL 20 described above, these components will not be described infurther detail.

In accordance with the principles of the present invention, IOL 40further comprises backstops 53 that rigidly support at least a portionof the circumference of each of haptics 48 and 49. Haptic contactsurfaces 54 of backstops 53 are coupled to a portion of the outersurface of each haptic 48, 49. Backstop 53 may be a cantilevered memberthat generally follows the substantially toroidal shape of therespective haptic. The portion of the circumference of each haptic 48and 49 supported by backstop 53 is chosen so that it is diametricallyopposed from the portion of the haptic that contacts the anterior walland/or equatorial portion of the lens capsule. Anterior end 55 of hapticcontact surface 54 ends approximately at the midline of haptic 48, i.e.,midway between the extreme anterior and the extreme posterior surfacesof the haptic. Posterior end 56 of haptic contact surface 54 extends tothe extreme posterior portion of the haptic such that approximately onequarter of the outer surface of haptic 48 is supported by the backstop.

During transition from the fully accommodated to the unaccommodatedstate, the anterior and posterior walls of the capsule retract towardthe equatorial portion of the lens capsule and compress the hapticaxially while the equatorial portion moves radially outward. Asdescribed above with reference to FIGS. 6A-6C, the portion of theanterior wall of the lens capsule translates a greater distance than thecorresponding portion of the posterior wall. The anterior wall thereforeis expected to impose a sufficiently large compressive load to actuateIOL 40. Backstop 53 provides a rigid surface that harnesses theasymmetric loads generated by the lens capsule during transition betweenthe accommodated and unaccommodated configurations.

Haptics 48 and 49 and backstops 53 may be configured so that haptics areplaced only in apposition (i.e., side by side contact) to the inner faceof the anterior wall, so that the increased motion of the anterior wallmay be fully utilized. Alternatively, these components may be configuredso that a portion of each haptic is placed in apposition to the innerface of the anterior wall while another portion is placed in appositionto an inner face of the posterior wall of the lens capsule.

Backstop 53 may be constructed from any suitable biocompatible materialknown in the art. For example, backstop 53 may be constructed from asuitable biocompatible polymer having a relatively higher rigidity thanthe haptic it supports. For example, backstop 53 may comprise a stiffermaterial or have a greater thickness or have a three dimensionalstructure that provides this higher rigidity. Backstops 53 may beinjection molded, machined, heat or pressure formed from a sheetmaterial, or by any other method known in the art. Each of backstops 53may be coupled to a respective haptic with a biocompatible adhesive,ultrasonic welding, or any other method known in the art. Backstops 53also may each include a flexible, foldable or hinged portionsubstantially adjacent to optic portion 41 of IOL 40, which permits thebackstops to be folded inward to simplify insertion into the lenscapsule.

Referring now to FIGS. 9A and 9B, an alternative embodiment of an IOLconstructed in accordance with the principles of the present inventionis described. IOL 60 generally includes optic portion 61 and hapticportion 62, both of which are similar in construction to thecorresponding portions of the embodiments described above. Inparticular, optic portion 61 includes anterior lens element 63, actuator64, intermediate layer 65 and substrate 66.

Haptic portion 62 includes haptics 68 and 69, each of which defineinterior volume 70 that is in fluid communication with channels and well72 that are formed in substrate 65. Because the structure of thecomponents is substantially identical to the corresponding structures ofthe previously described embodiment these components will not bedescribed in further detail.

Backstops 73 also are provided in IOL 60, and extend from optic portion61 to haptics 68 and 69. Backstops 73 may be generally shaped assections of a disk or cone. It will be appreciated that althoughbackstops 73 are shown as a solid member, the backstops also may includecavities or may have a web-like construction. It will be furtherappreciated that backstops 73 may be constructed to facilitateimplantation, and may include flexible, foldable or hinged sections.Alternatively, backstops 73 may be attached to optic portion 61 andhaptic portion 62 after the components are inserted into the lenscapsule.

The backstops may be configured to support any portion of thecircumference of the haptics so that they counteract compressive forcesplaced on the haptics in the anterior/posterior direction and/or theradial direction. In FIGS. 10A-10C, backstop 80 is configured to providea tangential support to haptic 81. Backstop 80 includes body portion 82and generally conical support surface 83 that is in tangential contactwith outer surface 84 of haptic 81, when haptic 81 is in an accommodatedor intermediate state. The orientation of haptic 81 with respect tobackstop 80 may be selected to provide desired compressioncharacteristics. For example, as shown in FIG. 10A, haptic 81 isoriented so that it has a major axis that is generally vertical, whichgenerally corresponds to being parallel to the optical axis of the IOL.As shown in FIG. 10B, haptic 81 may be oriented so that it has a majoraxis that is rotated with respect to the optical axis. It should beappreciated that haptic 81 may be oriented-at any angle with respect tothe optical axis of the respective IOL and the support surface 83 of therespective backstop 80. Support surface 83 of backstop 80 may beoriented such that support surface is cylindrical, conical or planar.

Once implanted and upon relaxation of the ciliary muscle, the lenscapsule exerts compressive forces F on haptic 81 that cause deformationof haptic 81, as shown in FIG. 10C. Because the anterior wall of thelens capsule is expected to generate a larger force due to its largertranslation near the equatorial portion, support surface 83 of backstop80 preferably is configured to directly oppose those forces.Accordingly, backstop 83 is positioned to prevent translation of thehaptic in response to forces applied by the anterior wall of the lenscapsule. Support surface 83 is configured so that it is conical,oriented generally perpendicular to the direction of force F and locatedon a side of haptic 81 opposite from the anterior wall of the lenscapsule. Tangential contact between accommodated haptic 81 and supportsurface 83 of backstop 80 will substantially deform haptic 81 duringposteriorly-directed motion of the anterior wall of the lens capsule.

With respect to FIGS. 11A and 11B, another embodiment of backstop 80 isdescribed that provides additional support to haptic 81. Backstop 80includes a curved support surface 83 configured to generally match thecurvature of outer surface 84 of haptic 81 in an accommodated state andto support a portion of the circumference of haptic 81. Illustratively,backstop 80 is configured to support approximately one quarter of outersurface 84 of haptic. It should be appreciated that haptic 81 may beoriented at any angle with respect to the optical axis of the respectiveIOL and the support surface 83 of the respective backstop 80.

The anterior wall of the lens capsule exerts forces F upon haptic 81 andbackstop 80 prevents posteriorly-directed translation of haptic 81,thereby converting the compressive load applied by the lens capsule to achange in the hydraulic pressure and moving the lens actuator. Theconfiguration of support surface 83 in FIG. 11 maintains the supportedportion of haptic 81 with a uniform shape, irrespective whether thehaptic is in the accommodated or unaccommodated state. The amount ofsupport provided by backstop 80 may be chosen for a desired deflectionof haptic 81 between the accommodated and unaccommodated states.

In yet another embodiment, depicted in FIGS. 12A-12D, a greater portionof haptic 81 is supported. In this embodiment backstop 80 is configuredto support a relatively large interior and posterior portion of haptic81. In particular, support surface 83 of backstop is configured togenerally match the curvature of accommodated haptic 81 and to supportapproximately half of the outer surface 84 of haptic 81. It should beappreciated that the orientation of haptic 81 with respect to theoptical axis of the respective IOL and the support surface 83 of therespective backstop 80 may be selected to provide desired compressioncharacteristics. FIGS. 12A-12C illustrate various orientations of haptic81 and FIG. 12D illustrates haptic 81 in an unaccommodated state.

Referring to FIGS. 13A and 13B, an additional embodiment of an IOLconstructed in accordance with the principles of the present inventionis described. Similar to the previously described embodiments, IOL 90generally includes optic portion 91 and haptic portion 92. Optic portion91 includes anterior lens element 93, substrate 96 and actuator 94interposed therebetween. In the present embodiment, actuator 94 alsoforms an intermediate layer and substrate 96 may function as a posteriorlens element.

Haptic portion 92 includes haptics 98 and 99, each of which definesinterior volume 100 that is in fluid communication with channels (notshown) and well 101 that are formed between actuator 94 and substrate96. Each haptic 98, 99 is integrated into substrate 96 and extendsbackstop portion 103 of substrate 96. Backstop 103 is configured toprovide support over a posterior portion of haptics 98, 99, similar tothe support provided by the backstop shown in FIGS. 12A-12D. It shouldbe appreciated that the dimensions of haptics 98 and 99 and backstopportion 103 are selected so that backstop portion 103 is significantlymore rigid than haptics 98, 99.

Additionally, load shelf 104 is provided on an anterior portion of eachhaptic 98, 99 that is approximately diametrically opposed to backstop103. Shelf 104 includes anterior surface 105 that is configured toengage a portion of the anterior wall of a lens capsule. Anteriorsurface 105 provides a greater surface area upon which force may beexerted on haptic 98, 99 by the lens capsule. As a result, energy frommovement of the capsular bag may be captured more efficiently andconverted into deformation of haptic 99, 98 and hydraulic forces withinIOL 90.

It should be appreciated that the backstops described herein may beformed as monolithic portions of any component of the respective opticportion, as shown in the embodiment of FIGS. 13A and 13B, or they may beseparate components that are mechanically coupled to the respectiveoptic portion, as shown in the embodiments of FIGS. 8 and 9.

In addition to utilizing backstops and/or load shelves and/or flanges toimprove the efficiency with which an IOL converts movement of the lenscapsule to hydraulic forces, spring forces throughout the IOL may bebiased. In particular, the spring forces created by the variouscomponents of the IOL may be tailored by selecting the elasticities ofthe components accordingly so that the force applied by movement of thecapsule may be amplified. For example, the elasticity of the hapticprovides one spring force, and the combined return force of the anteriorlens and actuator provides another spring force. The components may beselected so that one of those spring forces is stronger than the other.After the components are selected accordingly, the IOL may be chargedwith fluid during manufacture so that the fluid provides additionalforce that equalizes the unequal spring forces. Finally, introducing theIOL into a lens capsule may introduce an additional bias force. As aresult, energy is stored in the IOL that may be released during use toreduce the force that is required from movement of the capsule actuatethe IOL. In an exemplary embodiment, the anterior lens may be formed sothat in a relaxed state it is in an unaccommodated configuration and thehaptic may be formed so that in a relaxed state it is in an accommodatedstate. The pressure of the fluid may also be used to shift the biastoward either the accommodated or unaccommodated state.

It will be appreciated that the backstop of the foregoing embodimentsmay have a modular construction. For example, backstop may beimplanted—and then the optic and haptic portions may be subsequentlyimplanted as a unit and coupled to the backstop. This arrangement maysimplify the implantation procedure by allowing the IOL to be furthercompressed, thereby reducing the size of the incision needed to implantthe IOL.

A plurality of modular backstops 80, having different configurations andproviding different amounts of support, also may-be provided with anoptic portion and a haptic portion in a kit. Such a kit may be providedso that the amount of interior volume change of the associated hapticmay be selected by choosing a specific configuration of backstop. Forexample, if a maximum change in interior volume is desired, a backstopproviding tangential contact with a haptic may be chosen. Conversely, ifa minimum change in interior volume is desired, a backstop configured toprovide additional support may be selected. Such a kit also may beprovided so that an IOL may be custom fit to the anatomy of a particularpatient.

The support configurations of backstop 80 and haptic 81 described aboveare configured for a haptic that transitions between a small internalvolume in the accommodated state and a larger internal volume in theunaccommodated state. It should be appreciated, however, that use of thebackstop is not limited to this specific configuration of haptic.Instead, the haptic may have a cross-sectional shape that provides anydesired change in interior volume between the fully accommodated andfully unaccommodated states. Accordingly, the present invention also maybe used with haptics that decrease in volume when the haptic transitionsfrom the fully accommodated state to the fully unaccommodated state.

It further will be appreciated that the backstop may include stiffeningmembers. For example, stiffening members may be molded into backstops orotherwise coupled to backstops. Furthermore, such stiffening members maycomprise any material known in the art having a greater modulus ofelasticity than the backstop. A backstop also may be located such thatit counteracts the forces placed on the haptic by the posterior wall ofthe capsular bag, for example, where the forces applied by the posteriorwall of the capsular bag are sufficient to actuate the intraocular lens.

While preferred illustrative embodiments of the invention are describedabove, it will be apparent to one skilled in the art that variouschanges and modifications may be made therein without departing from theinvention. The appended claims are intended to cover all such changesand modifications that fall within the true spirit and scope of theinvention.

What is claimed is:
 1. An accommodating intraocular lens, comprising: anoptic portion including an anterior lens element and a posteriorsurface, a peripheral portion extending radially outward from the opticportion; and wherein the optic portion is adapted to deform to changethe power of the lens after being implanted in an eye; wherein theperipheral portion has a proximal portion secured to the optic portionand then extends away from the proximal portion and follows a radiallyouter periphery of the optic portion; wherein the peripheral portionincludes a radially inner backstop region that has a height dimension,measured in an anterior-to-posterior direction, that is less than agreatest height dimension of the peripheral portion, the backstop regionhaving a radially inner surface that protrudes radially inward relativeto a surface of a second peripheral portion region that is directlyadjacent to and anterior to the radially inner backstop region, theradially inner backstop region extending to the radially outer peripheryof the optic portion at a location that is spaced from where theproximal portion of the peripheral portion is secured to the opticportion, and wherein the backstop provides radially inner support forthe peripheral portion.
 2. The accommodating intraocular lens of claim1, wherein the peripheral portion also has a free distal portiondisposed away from the proximal portion.
 3. The accommodatingintraocular lens of claim 1, wherein the optic portion includes an opticfluid chamber.
 4. The accommodating intraocular lens of claim 3, whereinthe peripheral portion has a peripheral fluid chamber in fluidcommunication with the optic fluid chamber.
 5. The accommodatingintraocular lens of claim 1, wherein the anterior lens element isadapted to deform to change the power of the lens.
 6. An accommodatingintraocular lens, comprising: an optic portion; a peripheral portionextending radially outward from the optic portion; and wherein the opticportion is adapted to deform to change the power of the lens after beingimplanted in an eye; wherein the peripheral portion includes a radiallyinner backstop region that has a height dimension, measured in ananterior-to-posterior direction, that is less than a greatest heightdimension of the peripheral portion, the backstop region protrudingradially inward relative to a surface of a second peripheral portionregion that is directly adjacent to and anterior to the radially innerbackstop region, wherein the backstop provides radially inner supportfor the peripheral portion.
 7. The accommodating intraocular lens ofclaim 6, wherein the peripheral portion has a proximal portion securedto the optic portion.
 8. The accommodating intraocular lens of claim 7,wherein the peripheral portion extends away from the proximal portion.9. The accommodating intraocular lens of claim 7, wherein the peripheralportion follows a curved outer periphery of the optic portion.
 10. Theaccommodating intraocular lens of claim 7, wherein the peripheralportion has a free distal portion disposed away from the proximalportion.
 11. The accommodating intraocular lens of claim 6, wherein theprotruding radially inner backstop region extends to the optic portion.12. The accommodating intraocular lens of claim 6, wherein the opticportion includes an optic fluid chamber.
 13. The accommodatingintraocular lens of claim 12, wherein the peripheral portion has aperipheral fluid chamber in fluid communication with the optic fluidchamber.
 14. The accommodating intraocular lens of claim 6, wherein theoptic portion comprise an anterior lens element that is adapted todeform to change the power of the lens.